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Subjectlots of calls to __write/read_lock_failed
Running a webserver benchmark on 2.5.57, I saw some things in the 
profiles that I wasn't familliar with. Here's readprofile | sort | tail:

717 handle_IRQ_event 7.7935
732 do_gettimeofday 5.4627
755 __wake_up 10.7857
1089 del_timer 11.8370
1112 add_timer 7.8310
1500 system_call 34.0909
1847 schedule 2.4759
1873 kmap_atomic 12.8288
267475 __write_lock_failed 8358.5938
379837 __read_lock_failed 18991.8500
1044613 poll_idle 18010.5690
1704762 total 10.9631

I added a section at the ends of _raw_write_lock and _raw_read_lock
that look like this:

static int count = 0;
if( ++count%50000 == 0 ) {
printk("%s:%s() %d\n", __stringify(KBUILD_BASENAME),
__FUNCTION__, count );

file_table:_raw_read_lock() 3300000
Call Trace:
[<c0152469>] fget+0x9d/0xa0
[<c0152b27>] sys_fsync+0x21/0xbe
[<c0151b53>] sys_writev+0x47/0x56
[<c010931f>] syscall_call+0x7/0xb

filemap:_raw_read_lock() 1450000
Call Trace:
[<c0136937>] do_generic_mapping_read+0x411/0x43e
[<c0136d98>] file_send_actor+0x0/0x74
[<c0136e74>] generic_file_sendfile+0x68/0x76
[<c0136d98>] file_send_actor+0x0/0x74
[<c0151d48>] do_sendfile+0x1e6/0x28a
[<c0136d98>] file_send_actor+0x0/0x74
[<c0151e50>] sys_sendfile+0x64/0xcc
[<c010931f>] syscall_call+0x7/0xb

ip_output:_raw_read_lock() 2000000
Call Trace:
[<c02c90b2>] ip_finish_output2+0x154/0x226
[<c02c7466>] ip_queue_xmit+0x3dc/0x4ce
[<c011c71a>] default_wake_function+0x32/0x3e
[<c011c75e>] __wake_up_common+0x38/0x58
[<c02ddf24>] tcp_v4_send_check+0x54/0xe2
[<c02d81b6>] tcp_transmit_skb+0x2be/0x448
[<c02d54ca>] tcp_data_queue+0x23a/0x830
[<c02da693>] tcp_send_ack+0x81/0xb2
[<c02d68d1>] tcp_rcv_established+0x249/0x70e
[<c02defd1>] tcp_v4_do_rcv+0x12d/0x132
[<c02df452>] tcp_v4_rcv+0x47c/0x50c
[<c02c4363>] ip_local_deliver_finish+0x9f/0x19e
[<c02c4674>] ip_rcv_finish+0x212/0x29f
[<c02b410e>] netif_receive_skb+0xc2/0x17c
[<c02b4245>] process_backlog+0x7d/0x10c
[<c02b4395>] net_rx_action+0xc1/0x178
[<c01248e7>] do_softirq+0xb7/0xba
[<c010b390>] do_IRQ+0xec/0xf8
[<c0106eca>] default_idle+0x0/0x2e

time:_raw_write_lock() 1350000
Call Trace:
[<c010f321>] timer_interrupt+0x99/0x9c
[<c010b150>] handle_IRQ_event+0x38/0x5c
[<c010b330>] do_IRQ+0x8c/0xf8
[<c0106eca>] default_idle+0x0/0x2e
[<c0106eca>] default_idle+0x0/0x2e
[<c0109c8c>] common_interrupt+0x18/0x20
[<c0106eca>] default_idle+0x0/0x2e
[<c0106eca>] default_idle+0x0/0x2e
[<c0106ef4>] default_idle+0x2a/0x2e
[<c0106f6b>] cpu_idle+0x39/0x42
[<c01212a5>] printk+0x15d/0x190

Dave Hansen

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